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Cisco CCNA 640-802 Tutorials Part-4

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Importance of the levels of privilege in the Cisco IOS

Cisco IOS offers 16 privilege levels ( 0-15) for access to different commands or to make your router more secure.

The higher your privilege level mean the more router access you have and vice versa.

But most users or network administrators are familiar with only two privilege levels:

  • User EXEC mode—privilege level 1
  • Privileged EXEC mode—privilege level 15

or

  • privilege level 0 — Includes the disable, enable, exit, help, and logout commands.

  • privilege level 1 — Normal level on Telnet; includes all user-level commands at the router> prompt.

  • privilege level 15 — Includes all enable-level commands at the router# prompt.


By default you are in user EXEC mode (level 1) When you log in to a Cisco router.In this mode, you have access to limited information about the router, such as the status of interfaces, and you can view routes in the routing table. However, you can't make any changes or view the running configuration file.

By typing enable command takes you to level 15, privileged EXEC mode. In the Cisco IOS, In other words, you have full access to the router.

In bigger organization to properly manage and secure the router , Cisco gives the idea of levels

Configure the Levels

  • Show privilege: This command displays the current privilege. Here's an example:
router# show privilege
Current privilege level is 3
  • Enable: this command used to go to privileged EXEC mode. However, it can also take you to any privileged mode. Here's an example:
router# show privilege
Current privilege level is 3
router# enable 1
router> show privilege
Current privilege level is 1
router>
  • User: While this command configures users, it can also tell the IOS which privilege level the user will have when logging in. Here's an example:
router(config)# username test password test privilege 3
  • Privilege: This command configures certain commands to be available only at certain levels. Here's an example:
router(config)# enable secret level 5 level5pass
  • Enable secret: By default, this command creates the password to get to privilege mode 15. However, you can also use it to create passwords to get into other privilege modes that you create.

Cisco CCNP BSCI 642-901 Tutorials Part-8

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EIGRP Neighbor Relationship or Discovery and Route Exchange

The process of neighbor relationship or discovery and route exchange between two EIGRP routers is as follows:

  • First it send hellos to build a neighbor table.
  • The other router sends back a hello and an update(routing information)
  • First router acknowledges the update and sens its update
  • The other router acknowledges it

Hello packets are use as keepalives between the routers. Additional route information is sent only if a route is lost or a new route is discovered.

A neighbor is removed from the routing table if no hello is received within three hello periods (called the hold time). The default hello/hold timers are as follows:


5 seconds/15 seconds for multipoint circuits with bandwidth greater than T1 and for point-to-point media
60 seconds/180 seconds for multipoint circuits with bandwidth less than or equal to T1

Useful commands

  • debug ip eigrp
  • debug ip eigrp.
  • show ip eigrp neighbors.
  • ip hello-interval eigrp autonomous-system-number second
  • ip hold-time eigrp autonomous-system-number seconds

Glossary:

Neighbor:

Neighbors are directly attached routers that have a the following properties

  • Matching AS number
  • K values (the timers don’t have to agree).

Cisco CCNP BSCI 642-901 Tutorials Part-7

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EIGRP Messages


EIGRP uses various message types to

  • Initiate and maintain neighbor relationships
  • To maintain an accurate routing table.
  • In order to conserve bandwidth and router resources it sends messages only when needed, and those neighbors that need to receive them.

Packet Types

EIGRP uses five packet types:


  • Hello—Multicast for neighbor discovery/recovery.Identifies neighbors and serves as a keepalive mechanism.Require no acknowledgment. A hello with no data is also used as an acknowledgment (ack). Acks are always sent using a unicast address and contain a non-zero acknowledgment number.
  • Update—Reliably sends route information.Updates are used to convey reachability of destinations. When a new neighbor is discovered, update packets are sent so the neighbor can build up its topology table. In this case, update packets are unicast. In other cases, such as a link cost change, updates are multicast. Updates are always transmitted reliably.
  • Query—Reliably requests specific route information.Queries are sent when destinations go into Active state. Queries are always multicast unless they are sent in response to a received query. In this case, it is unicast back to the successor that originated the query. Queries are transmitted reliably.
  • Reply—Reliably responds to a a query.Replies are sent when destinations go into Active state.Replies are always sent in response to queries to indicate to the originator that it does not need to go into Active state because it has feasible successors. Replies are unicast to the originator of the query. Both queries and replies are transmitted reliably.
  • ACK—Acknowledgment. Request packets are used in route server applications. They can be multicast or unicast. Requests are transmitted unreliably.

Cisco CCNP BSCI 642-901 Tutorials Part-4

Filed under: by: Network World

What is Administrative Distance or How Router select the Best Path:

Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Administrative distance is a measure of the trustworthiness of the source of the routing information. Administrative distance has only local significance, and is not advertised in routing updates.

Route Source and its AD

Connected 0

Static 1


External BGP (Border Gateway Protocol) 20


Internal EIGRP (Enhanced IGRP) 90


IGRP (Internet Gateway Routing Protocol) 100


OSPF (Open Shortest Path First) 110


IS-IS (Intermediate System to Intermediate System) 115


RIP (Routing Information Protocol) 120


ODR (On Demand Routing) 160


External EIGRP 170


Internal BGP 200


Unknown 255



Cisco CCNP BSCI 642-901 Tutorials Part-3

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Selecting or Choosing Appropriate Routing Protocol

OSPF—Open Shortest Path First

Convergence: Fast

Protocol Type: Link-state, runs the Dijkstra algorithm to calculate the shortest-path first (SPF) tree

Update Timers: Only when Change occurs , on the other hand LSA Table is refreshed after 30 Sec

Metric:
Cost

Updates : Only Changes

Classless: Yes

VLSM Support:
Yes

Working: Develops adjacencies with its neighbors, periodically sending hello packets to neighbors, flooding changes to neighbors when a link’s status changes, and sending “paranoia updates” to neighbors every 30 minutes of all recent link state changes

Algorithm
:Dijkstra

Update Address: 244.0.0.5 (SPF routers)
244.0.0.4 (DR's and BDR's)

Protocol and Port:
IP Protocol and 89

Origin:
Based on RFC 2328

Where to Use:
Any network, small to very large


Cisco CCNP BSCI 642-901 Tutorials Part-2

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Selecting or Choosing Appropriate Routing Protocol

EIGRP—Enhanced Interior Gateway Routing Protocol

Convergence: Very fast

Protocol Type: Hybrid distance vector

Update Timers: Only when Change occurs

Metric: Delay, bandwidth, reliability, and load, using the Diffusing Update Algorithm (DUAL)


Updates : Only Changes

Classless: Yes

VLSM Support:
Yes

Working: Sends hello packets every five seconds to neighbors (can interoperate with IGRP) to see if the neighbors are still available; updates other routers by notifying them only when routes change

Algorithm
:DUAL

Update Address: 244.0.0.10

Protocol and Port:
IP Protocol and 88

Origin:
Based only on Cisco’s implementation, not an Internet RFC


Where to Use:
Any network, small to very large; all routers must be Cisco


Cisco CCNP BSCI 642-901 Tutorials Part-1

Filed under: by: Network World

How Router Build its routing Table

  1. For each route received from its interfaces, router verify the next hop. If it founds it invalid, then it discard the route.
  2. If multiple routes, valid routes are advertised by a routing protocol, it choose with the lowest metric.
  3. Routes are identical if they advertise the same prefix and mask, so 192.168.0.0/16 and 192.168.0.0/24 are separate paths and are each placed into the routing table.
  4. If more than one specific valid route is advertised by different routing protocols, choose the path with the lowest AD.

How to Set Password on Console , AUX and VTY lines

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Password set to Console mode

Router>enable
Router#configuration terminal
Router(config)#line console 0
Router(config-line)#password *****
Router(config-line)#login

Password set to Auxiliary port

Router>enable
Router#configuration terminal
Router(config)#line aux 0
Router(config-line)#password *****
Router(config-line)#login

Password set to Vty (Virtual Teletype-TELNET)


Router>enable
Router#configuration terminal
Router(config)#line vty 0 4
Router(config-line)#password *****
Router(config-line)#login

How to view Router Information

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View IOS version Router# show version
View current configuration file (RAM) Router# show running-config

View saved configuration file (NVRAM) Router#

show startup-config
View IOS version, size of IOS, and free space in FLASH Router# show flash
View CPU utilization Router# show processes cpu

View info about programs in RAM Router#

show processes
Display interfaces on router and their status Router# show interface
Display the ip interfaces on router and their status Router# show ip interface
Display which protocols are configured on the router Router# show protocol

Display ip protocol info Router#

show ip protocol

How to Choose a Cisco router that best fits your organization's needs

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Performance
Performance means how many packets per second the router could forward. For example, a Cisco 2600 series routers can forward an estimated 15,000 packets per second

Feature Upgradability

Router processors are rarely upgradeable, so this concerns to RAM and Flash.

Feature Expandability
Number of WAN and LAN interfaces supported by the router.

Software features
For example, you might need a router to support a certain interfaces for future or features like VOIP,QOS etc

Integrated services
This refers to functionality supported by a router that previously required separate boxes. For example, by adding a 16- or 32-port switching module in a router negates the need for an Ethernet switch; having a firewall, VPN server, and IDS/IPS sensor in a router can negate the need for a firewall, VPN concentrator, and dedicated IDS/IPS appliance.

Manageability
The router supports GUI interface, or is it command line only? Is there an interface available that allows you to manage multiple routers.

Redundancy
Redundancy is a critical feature for the network? Redundancy examples include hot-swappable power supplies or high-availability routing protocols such as HSRP or VRRP.

Support and reliability

Cisco traditionally offers a high level of support.

Cisco Switching Products Types

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Cisco offers two types of network switches

  • Modular switches
  • Fixed-configuration switches

Modular Switches

Cisco Catalyst modular network switches provide operational simplicity, media flexibility, and expandability to extend deployment life and reduce total ownership costs. Cisco switch products offer high availability, integrated security, strong support for converged applications, and significant long-term investment protection.

Fixed Configuration Switches

Cisco Catalyst fixed-configuration network switches offer exceptional performance, reliability, and serviceability in models for a wide variety of organization sizes.


Cicso Interview Questions with Answers

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Router Types:


Routers are of two types, Modular and Non-Modular


1.Modular

Routers will not have fix interfaces, can be added or removed whenever required.


2.Non-Modular
Routers will have fix interfaces, cannot be added or removed, they are fixed

Media:


There are 2 types of media


1.Guided media (wired media) 2.UnGuided media (wireless media)

1.Guided media (wired media)


e.g. Co-axial cable, twisted pair cable, fibre optics cable

2.UnGuided media (wireless media)


e.g. infrared, microwaves, radio waves,Infrared

View ACL Statistics in Cisco router or Switch

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Objectives:

Which ACLs are being used.
How many times an ACL entry (ACE) was used and on which interface.

Router# show access-lists ?
  <1-2699>           ACL number
  WORD               ACL name
  compiled           Compiled access-list statistics
  rate-limit         Show rate-limit access lists
  |                  Output modifiers
  

By number:


Router# show access-list 158

Extended IP access list 158

10 deny ip any any time-range denytime (active) (65951975 matches)


By name:


Router# show access-list MyACL
Extended IP access list MyACL
    10 permit tcp host 21.35.80.22 eq telnet host 21.23.77.101
    20 permit tcp host 21.35.80.25 eq 16100 host 21.23.77.101 (149407

Access-lists per interface and per direction:

Input ACL-

Router# show ip access-list interface FastEthernet 0/1 in Extended IP access list 150 in 10 permit ip host 10.1.1.1 any (3 matches) 30 permit ip host 10.2.2.2 any (12 matches)

Output ACL-

Router# show ip access-list interface FastEthernet 0/0 out Extended IP access list myacl out 5 deny ip any 10.1.0.0 0.0.255.255 10 permit udp any any eq snmp (6 matches)

CCNP Price Increase

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CCNP Exam price will increase from $225 to $300! Four exam option for CCNP certification – BSCI (642-901), BCMSN (642-812), ISCW (642-825), & ONT (642-845) remain at $150 USD each.